Random paving consists of different sized, individual blocks which are laid together so as to produce an irregular, unrepeated effect which is visually pleasing.
The problem encountered with random paving is the multiplicity of paving blocks which have to be first matched and then laid individually. Unfortunately, the finished appearance is entirely dependent on the skill of the person laying the paving; there is no guarantee that the end result will be in harmony with the environment and will achieve a sufficient level of randomness. Even with the most skilled and efficient layers, the time taken to lay such paving makes it extremely costly and all too often the ultimate result is not as aesthetically pleasing as random paving should be. Furthermore, there is a tendency with time and continued traffic for certain individual blocks to shift in relation to one another resulting in the occurrence of unsightly cracks, the effect usually being worsened by the subsequent growth of weeds through the cracks, which in turn further increases the crack size. The only way of satisfactorily halting such deterioration is to replace the whole area of paving, which solution is not only expensive but is also disruptive to traffic in its vicinity.
Despite these problems, random paving has enjoyed a come back in recent years, particularly in places which are being redeveloped and restored such as riverside, warehouse and docks areas, where old buildings or their facades are left in place. This is because random paving is in harmony and in keeping with and sympathetic to the old environment which has been newly restored.
For ease of laying, consideration has been given to producing a unitary paving blocks having markings on its upper surface to simulate random paving elements of different dimensions and with an external periphery having a shape which enables other similar blocks to be laid in opposite side to opposite side relationship. Moreover, U.S. Pat. No. Design 342,528 and U.S. Pat. No. 5,487,526 both to Hupp each discloses a patterned mould for moulding such unitary paving blocks in situ to create concrete pathways. The paving blocks are created by filling the mould with wet concrete in situ and subsequently removing the mould to reveal the paving blocks having surface impressions simulating the random paving. The mould has a periphery which enables it to be matched with the blocks previously formed in the wet concrete in opposite side-to-opposite side relationship.
Although careful laying of concrete using these moulds can overcome problems such as movement and resulting cracking, and hence the need for untimely replacement of individual random paving elements, the moulds still have the disadvantage that they cannot reproduce the irregular, unrepeated effect that can be obtained with individual paving elements. Moreover, this method of moulding wet concrete in situ still relies upon the skill of the layer and his speed of application.
This skill will involve subjecting the wet concrete to similar pressures for each moulding, otherwise too great a pressure might result in the mould cutting through the concrete bed and if too light might result in the impressions being too shallow thus failing to provide the desired aesthetically pleasing effect. Not only this, whole areas have to be fenced off to allow the concrete to set before it can be walked upon and the areas have to be covered to guard against the effects of rain.